1. Field of the Invention
The present invention concerns mercapto-silicone fluids. More particularly, the present invention relates to methods of preparation for mercapto-silicone fluids. Even more particularly, the present invention concerns methods of preparation of mercapto silicone fluids using mercapto-functional silanes.
2. Prior Art
The use of mercapto-functional silicone fluids has been well reported in the art. These fluids evidence utility as corrosion inhibitors and release agents, as described in U.S. Pat. No. 4,251,277, the disclosure of which is hereby incorporated by reference, as well as a component in fuser oils for photocopy machines, disclosed in U.S. Pat. No. 4,029,827, the disclosure of which is, also, hereby incorporated by reference.
Generally, these compounds have been prepared by mixing together a mercapto alkylalkoxysilane with water and, then, reacting the resulting solution with a mixture of a cycloalkylpolysiloxane and an end-blocked polyalkyl polysiloxane in the presence of an acid catalyst. When this mixture is heated, there is an equilibration of the components, together with the removal of water and alcohol, resulting in the formation of the mercapto-functional silicone fluid. This method is more particularly described in the aforementioned U.S. Pat. No. 4,251,277. While the products produced in accordance with this patent are efficacious, they are disadvantageous from a manufacturing standpoint, due to the relatively high cost of hexamethyltrisiloxane which is employed as the cyclic siloxane in the commercial product.
The present invention, as will subsequently be detailed, provides a new process for preparing mercapto-functional silicone fluids, which is based upon the hydrolysis of a polyalkylpolyalkoxysilane and a mercapto-functional silane. This method enables the formation of polymercapto compounds while employing less expensive cycloalkylpolysiloxanes.